Dynamics and quantification of dissolved heavy metals in the Mahanadi river estuarine system,India

Dynamics of heavy metals such as Fe, Mn, Zn, Cr, Cu, Co, Ni, Pb, and Cd in surface water of Mahanadi River estuarine systems were studied taking 31 different stations and three different seasons. This study demonstrates that the elemental concentrations are extremely variable and most of them are higher than the World river average. Among the heavy metals, iron is present at highest concentration while cadmium is at the least. The spatial pattern of heavy metals suggests that their anthropogenic sources are possibly from two major fertilizer plants and municipal sewage from three major towns as well as agricultural runoff. The temporal variations for metals like Fe, Cu, and Pb exhibit higher values during the monsoon season, which are related to agricultural runoff. Concentrations of Ni, Pb, and Cd exceed the maximum permissible limits of surface water quality in some polluted stations and pose health risks. Dissolved heavy metals like Fe, Mn, Cr, Ni, and Pb exhibit a non-conservative behavior during estuarine mixing, while Zn, Cu, and Co distribution is conservative. Distribution of cadmium in the estuarine region indicates some mobilization which may be due to desorption. The enrichment ratio data suggest that various industrial wastes and municipal wastes contribute most of the dissolved metals in the Mahanadi River. The Mahanadi River transports 18.216 × 10³ t of total heavy metals into the Bay of Bengal and the calculated rate of erosion in the basin is 128.645 kg km^− 2 year^− 1.     

Large-scale carbon stock assessment of woody vegetation in tropical dry deciduous forest of Sathanur reserve forest,Eastern Ghats,India

Tropical dry forests are one of the most widely distributed ecosystems in tropics, which remain neglected in research, especially in the Eastern Ghats. Therefore, the present study was aimed to quantify the carbon storage in woody vegetation (trees and lianas) on large scale (30, 1 ha plots) in the dry deciduous forest of Sathanur reserve forest of Eastern Ghats. Biomass of adult (≥10 cm DBH) trees was estimated by species-specific allometric equations using diameter and wood density of species whereas in juvenile tree population and lianas, their respective general allometric equations were used to estimate the biomass. The fractional value 0.4453 was used to convert dry biomass into carbon in woody vegetation of tropical dry forest. The mean aboveground biomass value of juvenile tree population was 1.86 Mg/ha. The aboveground biomass of adult trees ranged from 64.81 to 624.96 Mg/ha with a mean of 245.90 Mg/ha. The mean aboveground biomass value of lianas was 7.98 Mg/ha. The total biomass of woody vegetation (adult trees + juvenile population of trees + lianas) ranged from 85.02 to 723.46 Mg/ha, with a mean value of 295.04 Mg/ha. Total carbon accumulated in woody vegetation in tropical dry deciduous forest ranged from 37.86 to 322.16 Mg/ha with a mean value of 131.38 Mg/ha. Adult trees accumulated 94.81% of woody biomass carbon followed by lianas (3.99%) and juvenile population of trees (1.20%). Albizia amara has the greatest biomass and carbon stock (58.31%) among trees except for two plots (24 and 25) where Chloroxylon swietenia contributed more to biomass and carbon stock. Similarly, Albizia amara (52.4%) showed greater carbon storage in juvenile population of trees followed by Chloroxylon swietenia (21.9%). Pterolobium hexapetalum (38.86%) showed a greater accumulation of carbon in liana species followed by Combretum albidum (33.04%). Even though, all the study plots are located within 10 km radius, they show a significant spatial variation among them in terms of biomass and carbon stocks which could be attributed to variation in anthropogenic pressures among the plots as well as to changes in tree density across landscapes. Total basal area of woody vegetation showed a significant positive (R ² = 0.978; P = 0.000) relationship with carbon storage while juvenile tree basal area showed the negative relationship (R ² = 0.4804; P = 0.000) with woody carbon storage. The present study generates a large-scale baseline data of dry deciduous forest carbon stock, which would facilitate carbon stock assessment at a national level as well as to understand its contribution on a global scale.     

Residual behavior and risk assessment of flubendiamide on tomato at different agro-climatic conditions in India

Supervised field trials were conducted at four different agro-climatic zones in India to evaluate the dissipation pattern and risk assessment of flubendiamide on tomato. Flubendiamide 480 SC was sprayed on tomato at 48 and 96 g active ingredient (a.i.) ha^?1. Samples of tomato fruits were drawn at 0, 1, 3, 5, 7, 10, 15, and 20 days after treatment. Quantification of residues was done on a high-performance liquid chromatography (HPLC) device with a photo diode array detector. The limit of quantification (LOQ) of this method was found to be 0.01 mg kg^?1 while limit of detection (LOD) being 0.003 mg kg^?1. Residues of flubendiamide were found below the determination limit of 0.01 mg kg^?1 in 20 days at both the dosages in all the locations. The half-life of flubendiamide at an application rate of 48 g a.i.?ha^?1 varied from 0.33 to 3.28 days and at 48-g a.i. ranged from 1.21 to 3.00 days. On the basis of data generated under the All India Network Project on Pesticide Residues, a preharvest interval (PHI) of 1 day has been recommended, and the flubendiamide 480 SC has been registered for its use on tomato by the Central Insecticide Board and Registration Committee, Ministry of Agriculture, Government of India. The maximum residue limit (MRL) of flubendiamide on tomato has been fixed by the Ministry of Health and Family Welfare, Government of India under Food Safety Standard Authority of India, as 0.07 μg g^?1 after its risk assessment.     

Farmers perception and awareness of climate change: a case study from Kanchandzonga Biosphere Reserve,India

This study was an attempt to document the indigenous Lepcha people’s perception on climate change-related issues in five villages of Dzongu Valley located in Kanchandzonga Biosphere Reserve, India. Personal structured questionnaire was used for interview of 300 households selected randomly. Results showed that 85 % of the households have perceived climate change, mainly in the form of increasing temperature and unpredictable pattern of rainfall. In terms of climate change-related events, 75 % of the households believed that wind is becoming warmer and stronger over the past years. Majority of the households have observed changes in crop phenology, while about 90 % agreed that the incidences of insect pest and diseases have increased over the years, especially in their large cardamom crop. A comparison of community perceptions, climatic observations and scientific literature shows that the community have correctly perceived temperature change, unpredictable occurrence of rainfall and increased incidence of insect pest and diseases, which have largely influenced the experiences and perceptions regarding climate-related events. Results reveal that households have adopted the use of locally available material as mulches against soil erosion, to conserve the soil moisture and manage soil temperature. Majority of the households have diversified their cropping system through traditional agroforestry systems and intercropping. Unfortunately, most of the households were unaware about the scientific sustainable approaches to combating impact of climate change. This documentation will aid in assessing the needs in terms of actions and information for facilitating climate change-related adaptation locally in Sikkim state of India.     

Measuring Ammonia Concentrations and Emissions from Agricultural Land and Liquid Surfaces: A Review

Abstract

Aerial ammonia concentrations (C _g) are measured using acid scrubbers, filter packs, denuders, or optical methods. Using C _g and wind speed or airflow rate, ammonia emission rate or flux can be directly estimated using enclosures or micrometeorological methods. Using nitrogen (N) recovery is not recommended, mainly because the different gaseous N components cannot be separated. Although low cost and replicable, chambers modify environmental conditions and are suitable only for comparing treatments. Wind tunnels do not modify environmental conditions as much as chambers, but they may not be appropriate for determining ammonia fluxes; however, they can be used to compare emissions and test models. Larger wind tunnels that also simulate natural wind profiles may be more useful for comparing treatments than micrometeorological methods because the latter require larger plots and are, thus, difficult to replicate. For determining absolute ammonia flux, the micrometeorological methods are the most suitable because they are nonintrusive. For use with micrometeorological methods, both the passive denuders and optical methods give comparable accuracies, although the latter give real-time C _g but at a higher cost. The passive denuder is wind weighted and also costs less than forced-air C _g measurement methods, but it requires calibration. When ammonia contamination during sample preparation and handling is a concern and separating the gas-phase ammonia and aerosol ammonium is not required, the scrubber is preferred over the passive denuder. The photothermal interferometer, because of its low detection limit and robustness, may hold potential for use in agriculture, but it requires evaluation. With its simpler theoretical basis and fewer restrictions, the integrated horizontal flux (IHF) method is preferable over other micrometeorological methods, particularly for lagoons, where berms and land-lagoon boundaries modify wind flow and flux gradients. With uniform wind flow, the ZINST method requiring measurement at one predetermined height may perform comparably to the IHF method but at a lower cost.     

Physiological responses,tolerance, and remediation strategies in plants exposed to metalloids

Environmental Science and Pollution Research - Metalloids are a subset of particular concern to risk assessors and toxicologists because of their well-documented potential hazards to plant system....     

Arsenic tolerances in rice (Oryza sativa) have a predominant role in transcriptional regulation of a set of genes including sulphur assimilation pathway and antioxidant system

World wide arsenic (As) contamination of rice has raised much concern as it is the staple crop for millions. Four most commonly cultivated rice cultivars, Triguna, IR-36, PNR-519 and IET-4786, of the West Bengal region were taken for a hydroponic study to examine the effect of arsenate (As^V) and arsenite (As^III) on growth response, expression of genes and antioxidants vis-à-vis As accumulation. The rice genotypes responded differentially under As^V and As^III stress in terms of gene expression and antioxidant defences. Some of the transporters were up-regulated in all rice cultivars at lower doses of As species, except IET-4786. Phytochelatin synthase, GST and γ-ECS showed considerable variation in their expression pattern in all genotypes, however in IET-4786 they were generally down-regulated in higher As^III stress. Similarly, most of antioxidants such as superoxide dismutase (SOD), ascorbate peroxidase (APX), guaiacol peroxidase (GPX), catalase (CAT), monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR) increased significantly in Triguna, IR-36 and PNR-519 and decreased in IET-4786. Our study suggests that Triguna, IR-36 and PNR-519 are tolerant rice cultivars accumulating higher arsenic; however IET-4786 is susceptible to As-stress and accumulates less arsenic than other cultivars.     

Distribution and ecotoxicological concerns of persistent organic pollutants in sediment from creek ecosystem

In order to study the distribution and ecotoxicological concerns of persistent organic pollutants, grab sediment samples were collected from different locations across Thane creek, India. Analyses of samples were carried out using gas chromatography (GC)–electron capture detector and GC–mass spectrometry techniques. In organochlorine pesticides (OCPs), DDT (1,1,1,-trichloro-2,2-bis(p-chlorophenyl) ethane), DDE (1,1-dichloro-2,2-bis(p-chlorophenyl) ethylene), DDD (1-chloro-4-(2,2-dichloro-1-(4-chlorophenyl)ethyl) benzene) and α, β, and γ conformer of hexachlorocyclohexane (HCH), and 9 polychlorinated biphenyls (PCBs) congeners were analyzed in surface sediment samples. Concentrations of these pollutants in grab sediment samples may indicate their current use and impact on marine ecosystem. Average concentrations of total DDT (including DDD and DDE), HCH, and Σ₉PCBs were found to be 4.9, 12.5, and 2.9 µg kg^?1(dry weight) respectively. High concentrations of OCPs and PCBs were found at discharge locations in creek compared to other locations. Location-wise distribution of OCPs and PCBs indicates their high concentrations at the waste water receiving point. Data were compared for ecotoxicological impacts based on the levels specified in the sediment quality standards of the US Environmental Protection Agency and the Canadian Council of Ministers of the Environment. γ-HCH was found to have maximum potential to induce ecotoxicological impacts.     

Selection of suitable lichen bioindicator species for monitoring climatic variability in the Himalaya

Interspecific comparison in metals and PAHs profile in three lichen species, Flavoparmelia caperata, Phaeophyscia hispidula and Pyxine sorediata, were studied in different altitudinal gradients of the Western Himalayas. The species collected from 14 sites, enroute from Dehradun to Morinda (243 Km) including the trekking route 42 Km from Taluka to Morinda having an altitudinal gradient between 850–3,750 m, were analysed for their metals and PAHs. The species showed similar metal as well as PAHs profile under similar altitudinal gradients in the sequence of F. caperata > P. hispidula > P. sorediata. The difference in pollutant concentrations within each lichen species may be related to intrinsic attributes of the species, such as thallus morphology and the presence of lichen substances which are responsible for the sensitivity and accumulation potential of a particular species. Novelty of the present study lies on the fact that all the species show a similar efficiency of reflecting the environmental condition of the area, albeit the coefficient values of individual species for individual pollutant obtained by three-factor ANOVA revealed that the bioaccumulation affinity of F. caperata is significantly higher than P. hispidula and P. sorediata. For individual metals, F. caperata has a higher affinity for Al, Cr, Fe, Pb and Zn while P. hispidula has a significant positive affinity for Fe and Pb. PCA analysis of sites with respect to pollutant revealed the segregation of sites based on source and distance. Combining the bioaccumulation potential parameters along with geostatistical (GIS) techniques establishes that F. caperata species is a better accumulator of metals and PAHs in comparison to P. hispidula and P. sorediata in the temperate regions of the Himalaya.